To produce hydrogen by adding water to the vessel, receiving the collected plants and tightly sealing them therein, keeping them under dark or bright conditions.

This is a process for producing hydrogen and/or methane by tightly sealing plant bodies and water together in a vessel and the process is gentle to the environment. In addition, this process is simpler than the usual fermentation one using microorganisms and can produce hydrogen and/or methane in lower costs because the process does not need the preliminarily culture of microorganisms.